Developments in Hydroxypropylation of Starch: A Review

Abstract

Because hydroxypropyl starch (HPS) represents an important chemical modification of starch, extensive studies on hydroxypropylation are being carried out at various research centers worldwide. The present review summarizes development of methods for determination of the MS (molar substitution)/DS (degree of substitution) of hydroxypropyl starch, location of hydroxypropylation reaction sites in granules and on amylose and amylopectin molecules, and factors affecting reaction efficiency. Also presented is an overview of changes of physicochemical properties of starch that result from hydroxypropylation. Specifically reviewed are the effects of hydroxypropylation on granule morphology, crystallinity, thermal properties, swelling, and solubility; pasting, paste, and retrogradation properties; rheological and textural properties of HPS gels; and digestibility and uses of HPS.

Recent advances in starch‐based films toward food packaging applications: Physicochemical, mechanical, and functional properties

“…Enzymatic modification by pullulanase, an enzyme that cleaves (1,6)-α-D glycosidic linkages, can also effectively change the amylopectin to amylose ratio (Abidin et al, 2018; Although most of these modification strategies involve fairly simple synthetic reaction steps, much attention has recently been focused on developing and optimizing processes for reactive extrusion of starch, opening the door for further commercialization of starch-based products (Fitch-Vargas et al, 2019;Fonseca-Florido et al, 2019;Jebalia et al, 2019;Kaisangsri, Kowalski, Kerdchoechuen, Laohakunjit, & Ganjyal, 2019;Liu et al, 2019;Milotskyi, Bliard, Tusseau, & Benoit, 2018;Nessi et al, 2019;Siyamak, Laycock, & Luckman, 2020;Tian, Zhang, Sun, Jin, & Wu, 2015;Ye et al, 2019). Although chemical modification of starch typically diminishes the mechanical properties of the resultant films by causing less efficient polymer packing and subsequent decreases in film crystallinity, modified films can exhibit some improvements in some mechanical properties (Table 2, entries 40 and 41) as well as oftentimes leading to better barrier properties or increased compatibilization with additives that can offset the decrease in properties (Table 2, entries 10 and 38) or can endow the film with additional function while decreasing the potential for retrogradation (Colussi et al, 2017;Fu et al, 2019). Outcomes largely depend on the modification type, the extent of modification (which also depends on the starch type as amylose is more reactive to most modification strategies compared to amylopectin), and other components in the film formulation.…”

“…One common method involves the use of (3‐chloro‐2‐hydroxypropyl)trimethylammonium chloride (CHPTAC) (Figure 4b) (Bayat Tork, Khalilzadeh, & Kouchakzadeh, 2017; Butrim, Bil'dyukevich, Butrim, & Yurkshtovich, 2016; Huang et al., 2019). Some other strategies that have been commonly applied to cellulose have also been applied to starch, to include carboxymethylation (Cai et al., 2019; Jiang et al., 2019; Li, Wu et al., 2019; Zhang, Pan et al., 2017; Zhang, Chi et al., 2017; Zhang, Tao, Niu, Li, & Chen, 2017), hydroxypropylation (Fang, Fu, Tao, Liu, & Cui, 2020; Fu, Zhang, Ren, & BeMiller, 2019; Hu, Jia, Zhi, Jin, & Miao, 2019; Shaikh, Ali Tahira, Hasnain, & Haider, 2019) (Figure 4c), and oxidation (Li et al., 2020; Wang et al., 2015; Zhang, Ding, Gu, Tan, & Zhu, 2015; Zhao et al., 2015). Oxidation of C6 hydroxyl groups with catalytic TEMPO and bleach can be accomplished in a facile and environmentally friendly route in aqueous media (Figure 4d).…”

Physicochemical Properties of Hydroxypropylated Apios Starches

“…The content of hydroxypropyl groups (HPs) in the starch was calculated from the standard curve using propylene glycol standard solution. The degree of substitution (DS) was calculated by converting the HP results ( Johnson, 1969 ; Fu et al, 2019 ).…”

Modification of Starches with Different Amylose/Amylopectin Ratios Using the Dual Approach with Hydroxypropylation and Subsequent Acid‐Thinning: II. Impacts on Gelatinization and Solution Properties

“…[ 4,5 ] A comprehensive review was recently given by Fu et al. [ 6 ] The granular state of the starch and the semicrystalline structure and its type are generally preserved, and the molecular size being basically not reduced during HP is commonly accepted. [ 6 ] However, the reliable determination of the molecular composition of HP starches is very challenging and sophisticated, and the impact of the HP on the molecular starch structure strongly depending on the starch type was evidently shown recently.…”